The Stanley 6-Inch Classic 99 Retractable Utility Knife starts sharper and stays sharper than standard heavy-duty blades. This knife features a patented interlocking nose to hold the blade securely. The three-position, retractable blade can be stored in the handle. This knife includes three blades and comes with Stanley's limited lifetime warranty. Everyone knows the importance of the right tool for the job. Stanley's "Application Specific Blades" are designed with unique features for cutting drywall, roofing shingles and paper. Each blade is constructed of carbon alloy steel. With Stanley's patented S3 Technology, paper blades start sharper and stay sharper, roofing blades are stronger, and drywall and paper blades deliver more cuts per blade. The entire line provides better performance than standard heavy duty blades. View the comparison chart to choose the Stanley blade that is right for you.